1. Field of the Invention
The present invention relates generally to the art of spring motors useful for a variety of applications, including venetian blinds and window shades. More specifically the present invention relates to a system in which lifting cords and cord locking mechanisms are eliminated from shades or blinds. Still more specifically, the invention relates to window covering systems which employ one or more constant or consistent, variable force springs to balance the weight of accumulated window covering material, depending upon the extent to which the blind or shade is raised or lowered. The present invention also relates to motorized blinds and shades.
2. Description of the Prior Art
Venetian blinds have been known for many years and typically include a plurality of slats made from metal, plastic, wood or other materials and supported by ladders. Such blinds typically include a bottom bar and a tilt mechanism to cause the slats to move from a horizontal position to a nearly vertical position to open and close the blinds with respect to the passage of light. It is also conventional with such systems to use lifting cords coupled to the bottom bar, passing through the slats and into mechanisms within the blind headrail. The cord is used to raise the bottom bar, accumulating individual slats as the bar is raised. Because of the natural tendency of the bar and accumulated slat weight to free fall, locking mechanisms are also commonly employed with such prior art devices. Pleated and other types of shades also include a bottom bar and similar raising, lowering, and cord locking mechanisms.
Several attempts have been made to eliminate the lifting cord locks, some of such attempts going back nearly 140 years. See, for example, Bixler, U.S. Pat. No. 13,251, issued Jul. 17, 1855 for xe2x80x9cInside Blinds.xe2x80x9d In this device, a pair of xe2x80x9cfuseesxe2x80x9d are employed, namely spirally grooved pulleys, to wind a cord passing therebetween. The two fusees are arranged so that as a barrel spring is being wound the cord joining the fusees compensates for changes in spring force. A spool is provided for accumulation of the lifting cord.
U.S. Pat. No. 2,420,301, issued May 13, 1947 to Cusumano for xe2x80x9cVenetian Blindxe2x80x9d also employs a cone-shaped member with grooves and an elongate coil spring. This design dispenses with normal draw cords and provides a counterbalance so that the slats may be retained at any vertical position without a lock or anchorage and so that the blinds can be raised with relatively small effort.
A different device is shown in Pratt""s U.S. Pat. No. 2,324,536 issued Jul. 20, 1943 for xe2x80x9cClosure Structure.xe2x80x9d In this device, tapes and coil springs are employed to raise and lower a blind particularly suited for use in a vehicle such as a train. The complex structure disclosed in this patent is especially suitable for devices in which the bottom bar and the slats ride in tracks as they move upwardly and downwardly.
Other patents show various spring devices used with venetian blinds. For example, in Cohn""s U.S. Pat. No. 2,390,826, issued Dec. 11, 1945 for xe2x80x9cCordless Venetian Blinds,xe2x80x9d two coil springs are used to provide even force, with a centrifugal pawl stop. The blind is raised by freeing the pawl to allow the spring to provide a lift assist. Other more conventional systems employing springs and ratchet and pawl mechanisms include those shown in Etten""s U.S. Pat. No. 2,824,608, issued Feb. 25, 1958 for xe2x80x9cVenetian Blindxe2x80x9d; U.S. Pat. No. 2,266,160, issued Dec. 16, 1941 to Burns for xe2x80x9cSpring Actuated Blindxe2x80x9d; and U.S. Pat. No. 2,276,716, issued Mar. 17, 1942 to Cardona for xe2x80x9cVenetian Blind.xe2x80x9d
Various attempts have also been made in the prior art to motorize blinds and shades. In most of these systems hard wiring is required because larger motors are required to move the bottom rail and accumulated window material.
None of the aforementioned patents disclose the use of spring motors of the type disclosed herein to eliminate the conventional pull cords and locks of venetian blinds or shades in a simple and easily adaptable mechanism having few components parts. A system which overcomes the disadvantages of the more complex and cumbersome systems of the prior art would represent a significant advance in this art.
The present invention features a cordless blind or shade in which a spring motor is used to eliminate conventional pull cord and cord-lock mechanisms.
The present invention also features a system in which either the spring strength or the number of spring motors may be altered, depending upon the size of the window covering. The invention further features techniques for increasing the friction on the cords used to raise and lower the blinds or shade to assist in maintaining a desired position against any spring force which may exist through the range of travel of the bottom bar.
The present invention still further features a system which is easy to adapt to a wide variety of blind or shade designs and sizes and the capability of applying spring forces in a variety of ways and combinations.
A different feature of the present invention is the use of spring motors and small electric motors to provide highly desirable automatic or remote controlled capabilities for shades and blinds.
How the present invention accomplishes these features will be described in the following detailed description of the most preferred embodiments, taken in conjunction with the FIGURES which illustrate blind systems, although shade applications are also enhanced by the present invention. Generally, however, the features are accomplished by employing constant force or consistent variable force spring motors in a blind or shade system, while eliminating conventional pull cord and associated cord-lock mechanisms. The features are accomplished by using springs wound on drums, the springs being of constant cross-section (constant force) or varying in width, thickness, or both along their length (variable force) whereby spring force imparted to a coiled spring is transferred from one drum to another. For these spring motors, such force is at its highest level when the blind or shade is fully raised, i.e., when the cords are supporting the full weight of the window covering. The spring force is at its lowest point when the window covering is fully lowered and, in the case of blinds, the slats are being individually supported by ladders, rather than by the cords, leaving only the bottom bar to be supported by the cord. In constant force systems, the spring force is substantially constant throughout the range of movement of its shade or blind bottom rack. The blinds and shades of the present invention may be manipulated by the operator simply grasping the bottom bar and urging it in an upward or downward direction.
The features of the present invention are also accomplished by providing selection criteria for the springs, to take into account the size and weight of a particular blind or shade or by adding additional spring motors for heavier or wider window coverings. To achieve greater certainty in maintaining desirable spring forces, in a most preferred, alternate form of the invention, the spring motors are interconnected to ensure that they operate in unison to provide a level action throughout the range of blind or shade travel. All of these features are accomplished in a blind or shade which will remain in the position selected by the user and which in a preferred embodiment may be motorized, e.g. by a small remote controlled DC motor. In an illustrated embodiment, friction imparting devices are, if necessary, used with the cords coupling the bottom bar and a spool within the headrail.
Other features of the invention, and other ways in which those features are accomplished, will become apparent to those skilled in the art after the detailed description of the most preferred embodiment is read and understood. Such other ways are deemed to fall within the scope of the invention.